The Tricon Turbine Control System - Invensys

White PaperThe Tricon Turbine Control SystemA Field-Proven Triple Modular Redundant (TMR) Digital Systemfor Turbine Control and Safety Application in Nuclear Power PlantsAuthor: Naresh Desai, Sr. Technical Consultant, InvensysWhat’s Inside:1. Abstract2. Introduction3. Major Requirements4. Tricon Architecture5. Critical Application Software Architecture6. Operator Screens7. Summary

The Tricon Turbine Control SystemA Field-Proven Triple Modular Redundant (TMR) Digital Systemfor Turbine Control and Safety Application in Nuclear Power Plants1. AbstractThe Triconex® Tricon is a Triple Modular Redundant (TMR) digital system for turbinecontrol and safety application in nuclear power plants (NPPs). The steam turbine is a criticalelement in the continuous operation of NPPs. When a turbine goes offline, the entireplant goes down. Poor reliability of the existing obsolete control system is one of themajor causes of turbine trips. A single component failure can result in a turbine shutdown,causing unscheduled plant outages that cost hundreds of thousands of dollars per day inmaintenance costs and lost revenue. The Tricon is a high reliability and high availability(99.99%) turbine control system with no single point of failure. It provides an economicalsolution to the obsolescence, reliability and availability problems, while improving theoperational efficiency of NPPs.2. IntroductionTurbine control systems are critical for the safe, efficient and continuous operation of anNPP. Existing control systems are old, obsolete, unreliable and hard to maintain due toTriconex Triconthe unavailability of spare parts. The staff at NPPs should not spend time trying to keepantiquated control systems running. The design and architecture of a critical control system should incorporate high reliability and highavailability as inherent attributes. This type of control system allows the plant operator to focus on the plant behavior, monitoring fieldparameters critical to maintaining the plant and quickly perform corrective actions when necessary.Aging turbine control systems must be replaced with high reliability and high availability, modern digital control systems, sounnecessary turbine trips and plant outages can be prevented. New turbine control systems must be easy to operate, maintain,upgrade and expand in the future.Nuclear power plants have various types of turbines from different vendors. Many turbines are reheat steam turbines that vary insize from a few hundred megawatts (MWs) to over 1000 MWs. Most monitoring, control and safety requirements are common to allturbines from different vendors. A turbine control system must have the capabilities and flexibility to handle common requirementsand vendor-specific requirements for all turbines.3. Major RequirementsReliability, Availability and Maintainability• High reliability and high availability with no single point of failure for continuous plant operation• Online diagnostics with more than 99.9% coverage• Online repair• Easy to maintain, modify and add future enhancements• Easy to upgrade and expand in the future without affecting existing field elements and wiringField Interface• Interface to the existing and new field elements for the turbine, if required.• Interface with other control systems throughout the plantControl, Safety and Test• Implement existing automatic or manual operational procedures and control strategies• Implement manual or automatic turbine chest and shell warm-up, turbine generator synchronization• Perform online valve tests (main control valves, main stop valves, reheat stop valves and intercept valves) and over speed detectiontest under operator control• Detect and safely shut down the system when unsafe plant conditions arise. Unsafe conditions include: turbine overspeed, loss oflube oil pressure, bearing temperature, vibration abnormalities, power load unbalance (PLU)• Automatic switching between speed control state (mode) to load control state, depending on the plant conditions• Droop control for speed and/or load stability• Automatic switching between full arc and partial arc (single valve mode and sequential valve mode) operationPage 1

The Tricon Turbine Control SystemA Field-Proven Triple Modular Redundant (TMR) Digital Systemfor Turbine Control and Safety Application in Nuclear Power PlantsOperator Interface• Easy to use operator interface for monitoring and control• Enhanced visibility of critical turbine parameters in real-time• Easy navigation between the control, monitoring, maintenance and test screensCommunications• Ability to interface with existing plant computer and/or DCS system• Redundant, high-speed, industry standard communication interfaces and protocols to transfer real-time data (such as turbineparameters, field status, alarms, trips, system status, field inputs and outputs) for control, monitoring, logging and trending for fielddiagnostics purposesThe Tricon satisfies the above requirements for turbine control in NPPs. The Tricon overall architecture is presented in Figure 1. Thisbasic architecture can be adapted to satisfy existing plant-specific field elements and wiring requirements, additional field elementrequirements, existing auto-manual turbine control procedures and strategies and communications requirements.4. Tricon ArchitectureA typical Tricon system consists of the following:• Tricon TMR system• TriStation 1131 application development station• Turbine control application software• I/A Series® or Wonderware® HMI (Human Machine Interface)• Maintenance workstation• TriLogger softwareA brief summary of the Tricon system components is provided below.Tricon SystemThe Tricon is a TMR architecture based digital safety and control system. The system is certified by TÜV (a world-recognized,independent safety agency) at International Electrotechnical Commission (IEC) Safety Integrity Level 3 (SIL) to be used for safety andcritical control applications in process control and other industries. The Tricon is also certified by the Nuclear Regulatory Commission(NRC) to be used for safety (1E) and critical control applications in NPPs.The Tricon has three independent channels from the input terminal to the output terminal. Each input is scanned and voted by thethree main processors (MPs) and the resultant voted input is provided to the same application running in the three MPs. The outputsfrom the application running in each MP go to the output modules where they are voted. The resultant voted output for each pointgoes to the output terminal/field device.The TMR architecture and design allows the Tricon system to perform its intended safety and control functions in the presence of asingle hardware fault. In addition, the design allows the Tricon to run in TMR, DUAL, or SINGLE mode, thus providing high availability(99.99%). The built-in online diagnostics provide more than 99.9% fault coverage and can isolate a fault to a specific module. Thefaulted module can be replaced with a new module online without affecting the turbine operation. The Tricon combines technologyand architecture features to provide safety and control functions with the high reliability and high availability required for the safetyand critical control applications NPPs.Page 2

The Tricon Turbine Control SystemA Field-Proven Triple Modular Redundant (TMR) Digital Systemfor Turbine Control and Safety Application in Nuclear Power Plants6. Operator ScreensThe following standard turbine control and monitoring screens with security levels are available for both the I/A Series workstation andthe Wonderware workstation. These standard screens can be modified and/or additional screens can be easily developed to meetnuclear plant operational requirements.• Main Menu Screen• Turbine Overview Screen• Turbine Start-up Screen• Normal Operation Screen• Turbine State (mode) Screen• Valve Tests Screen• Alarms and Trips• Maintenance and DiagnosticsPage 7

The Tricon Turbine Control SystemA Field-Proven Triple Modular Redundant (TMR) Digital Systemfor Turbine Control and Safety Application in Nuclear Power Plants7. SummaryInvensys is a customer-centric company that provides a complete solution to the nuclear industry for safety and critical control.Invensys has installed more than 1,500 turbine control systems in plants all over the world, including NPPs.The Tricon is a high reliability, high availability (99.99%), digital turbine control system with no single point of failure. The built-infeatures of the Tricon (high reliability, high availability, low maintenance, self-calibration, built-in online diagnostics, online repair, easyto expand and upgrade) help reduce life cycle operations and maintenance costs.The built-in online diagnostics provide more than 99.9% diagnostic coverage, providing a basis to potentially reduce periodicsurveillance testing between refueling cycles. Online repair increases availability even further, as turbines are not required to beshutdown to perform repairs.The Triconex Tricon solves the obsolescence, reliability and availability problems of NPPs, while improving the operational efficiency ofthe NPP.With a Tricon installation, you not only receive proven TMR technology, but the experience and knowledge of the Triconex turbinecontrol domain experts spanning over a quarter of a century in the industry. Triconex experts have seen and resolved many problemsassociated with the installation and operation of turbine control systems. If you experience problems with the installation or operation,it is highly probable that Triconex experts know about the problem and are ready to help you solve it. With Invensys you gainexperience in design, development, installation and support of the turbine control system, efficient project execution and integrationcapabilities, round-the- clock customer support and customized training for the I&C and plant operation personnel. The Tricon will bethe last system you will ever have to install for turbine control. Future expansions and upgrades can be completed in one or two days,not weeks. Existing cabinets, term panels, or field wiring do not need upgrading. This means you don’t have to perform continuitytests, loop checks, or recalibrations. The overall result is tremendous cost savings in expansion or upgrades, project managementefforts and reduced outage duration.Invensys Operations Management • 5601 Granite Parkway III, #1000, Plano, TX 75024 • Tel: (469) 365-6400 • Fax: (469) 365-6401 • iom.invensys.comInvensys, the Invensys logo, ArchestrA, Avantis, Eurotherm, Foxboro, IMServ, InFusion, SimSci-Esscor, Skelta, Triconex, and Wonderware are trademarks of Invensys plc, its subsidiaries or affiliates.All other brands and product names may be the trademarks or service marks of their representative owners.© 2010 Invensys Systems, Inc. All rights reserved. No part of the material protected by this copyright may be reproduced or utilized in any form or by any means, electronic or mechanical, includingphotocopying, recording, broadcasting, or by any information storage and retrieval system, without permission in writing from Invensys Systems, Inc.Rel. 10/10PN TR-0118Page 8